#include<bits/stdc++.h>
using namespace std;

int arr[100];

int main(){
    int n;
    cin>>n;

    arr[0] = 1;
    arr[1] = 1;

    for(int i = 2; i<=n; ++i){
        arr[i] = arr[i-1] + arr[i-2];
    }

    cout<<arr[n]<<endl;
    return 0;
}